Manufacture of tubes



March 31, 1970 J. MARCOVITCH 3,503,238

MANUFACTURE OF TUBES Filed May 1. 1967 6 Sheets-Sheet 1 March 31, 1970 J. MARCOVITCH 3,503,238

MANUFACTURE OF TUBES Filed May 1, 196'? 6 Sheets-Sheet 2 w mH . I z/ av AWE/W deems Mmecowrw/ a, fm *JM March 31, 1970 J. MARCOVITCH 3,503,238

MANUFACTURE OF TUBES Filed May 1, 1967 I 6 Sheets-Sheet 3 March 31, 1970 J. MARCOVITCH 3,503,238

MANUFACTURE OF TUBES Filed May 1, 1967 6 Sheets-Sheet 4 Avwwme 0 4605 M64 00! rcw March 31, 1970 J. MARCOVITCH MANUFACTURE OF TUBES 6 Sheets-Sheet 5 Filed May 1 1967 Jame M/mcow row March 31, 1970 J. MARCOVITCH MANUFACTURE OF TUBES 6 Sheets$heet 6 Filed May 1. 1967 Jncaa MA/ecawru/ United States Patent 3,503,238 MANUFACTURE OF TUBES Jacob Marcovitch, Johannesburg, Transvaal, Republic of South Africa, assignor to Rotary Profile Anstalt, Vaduz, Liechtenstein Filed May 1, 1967, Ser. No. 634,943 Claims priority, application Republic of South Africa, May 5, 1966, 66/2,610; Aug. 17, 1966, 66/4,911 Int. Cl. B21b 19/04, 25/00 US. CI. 72-96 Claims ABSTRACT OF THE DISCLOSURE Tubular articles are made by drawing a billet through an annular throat one wall of which is defined by a series of skewed rollers the contour of each of which is such as to make line contact with the tube traversing the throat, and to draw material from the billet through the throat. The billet may be annular, and it may be continuously made from molten metal replenished from a reservoir.

This inventionrelates to the manufacture of tubular articles by the method commonly known as rotary piercing in which a billet is offered to a piercing head which is rotated and advanced relatively to the billet to form the cavity of the article, while the formed tube is supported. In the manufacture of tubing, recourse has been had to this method, the billet being annular and drawn over the head to pass through an annular throat defined between the head and a series of skewed rollers disposed radially around the head. The billet is nipped by the rollers which, by reason of their rotation and their oblique location relatively to the billet, cause the billet to be advanced through the throat continuously and pierced to form a tube.

The method has grave disadvantages. One of them is that the head has to be maintained in position as the drawing of the tube proceeds. As the billet is solid, the only way to mount the head is at the end of a stem over which the drawn tube passes, in its advance towards the supported end of the stem, and which fullfils the function of supporting the formed tube. Unless the finished tube is of short length, which is seldom the case, the stem has to be long, and it tends to whip in use, which causes the shape of the throat to vary and therefore affects the uniformity of the wall thickness of the tube. It is true that the stem can be journalled in a series of removable bearings, but, as they must be successfully withdrawn to make way for the advancing tube, they add to the complication of the machine without being of much help. So serious is this disadvantage that tube made by the piercing method is sold with the maximum permissible variation in wall thickness given, and this can be as high as 33%. It follows that if uniformity of wall thickness is of moment to the user, the tube has to be processed, which adds to the cost and wastes material.

The object of the present invention is to provide a piercing technique which minimizes the difficulties and inconveniences of the standard techniques, and to make it possible to finish the product to its desired dimensions, configuration and finish in one combined operation, and to introduce new means to achieve this.

According to the invention, apparatus for manufacturing tubular articles consists of a cantilevered forming head, an annular throat which is located close to the attachment of the cantilevered head, and the inside of which is defined by the head, structure surrounding the head and defining the outside of the throat, and means to draw plastically deformable material from a billet through the throat.

3,503,238 Patented Mar. 31, 1970 With the construction described above, the support for the head can be made massive, as the head diameter is not limited by the inner diameter of the drawn tube. The support can itself be massively supported, as it extends rearwardly beyond the billet and can be cantilevered in a sturdy mounting. The drawn tube, not having the stem within it, can be of indefinite length, depending only upon the volume of material contained in the billet. Indeed, where the billet is formed in situ from constantly supplemented molten material, the length of the tube can theoretically be infinite.

In the conventional techniques, the rollers always surround the advancing tube, and this limits the size of tube that can be drawn, because amongst other reasons, the power requirements of the piercing process become far too great for any but fairly small bore tubes. In the present invention, however, the degree of deformation required to produre large diameter tubes can be mitigated by increasing the aperture size of the billet. The tube diameter can, indeed, be so large as to permit the rollers to be located within the cavity of the advancing tube. There is then no restriction whatever as to the massiveness of the structure surrounding the head, but the support for rol ers in the head is circumscribed.

Where the tubular article to be made has a closed end, the technique of drawing a preformed billet over the piercing head is not possible, as this presupposes the annular billet open at both ends. Therefore, for the closedended articles, the billet is initially a solid slug which is pierced by the piercing head to form a blind hole, and the billet is then propelled through the throat by the head. In either case, however, the procedure of forming the billet in situ from a constantly replenished source of molten material is valid.

Embodiments of the invention are illustrated in the accompanying drawings, in which:

FIGURE 1 is a vertical section through a machine for making long lengths of tubing,

FIGURE 2 is a vertical section of part of a machine for making lengths of tubing of fairly large bore,

FIGURES 3, 4 and 5 are detail views showing suitable configurations of rollers, I

FIGURE 6 is a side view, partly in section, of a machine for making long lengths of tubing from metal that is initially molten,

FIGURES 7 to 11 are fragmentary side views, all but 7 partly in section, illustrating the manufacture of a tubular article with one end closed, and, in FIGURE 11, with both ends closed,

FIGURE 12 is a fragmentary side view, partly in section, of a machine to make a tube with a closed end, and

FIGURE 13 is a fragmentary sectional view of apparatus to make a closed-ended article such as a flanged dome.

For the making of long lengths of tubing, two basic embodiments are shown in FIGURES 1 and 2, FIG- URE l for smalland FIGURE 2 for large-bore tubing. In FIGURE 1, the head 10 is the tip of a massive rod 12 journalled in a bearing block 14. The tip is reduced in diameter and joins the body of the rod in a smooth curve 16. The head is surrounded by a series of skewed rollers 18 mounted in a cage 20 that is itself journalled within a massive bearing block 22. The cage is rotated by a gear drive 24. Alternatively the rollers may be mounted on axles carried by the cage or may roll on a backing surface.

There is defined between the bearing blocks 14 and 22 an annular space surrounding the rod 12 and in which is located an annular billet 26. Circumferentially, the space may be enclosed by a sleeve shown in dotted lines at 28, which may be divided into segments which are movable radially inwardly to pummel the billet to maintain it in contact with the head. Pushers 30 are provided to propel the billet towards the throat defined between the rollers and the head by pressure on a backing plate 31. The billet is preformed with an annular lip 32 which is projected into the throat by the pushers to be nipped between the head and the rollers. Thereafter, the billet is drawn through the throat by the nip of the rollers and emerges as a tube 34. In the case of a convergent throat, such as that illustrated, the billet is preformed complementally to the rod 12.

The pushers may be used continuously as the tube is drawn, to assist the advance of the billet towards and through the throat. On the other hand, the pushers may be used only as an initial feeder, and the rollers alone used to advance the formed tube, if the nature of the material and of the tube make this practicable.

In FIGURE 2, the structure 36 surrounding the head is a circular collar. Within it is a post 3 8 on which is rotatably mounted a cage 40 that houses a series of skewed rollers 42. The cage is rotated by a gear 44 on a shaft 46. The shank 47 of the post is surrounded by a collar 48. This composite structure forms a head in which the rollers 42 are mounted.

The billet 50, again annular, is confined within a space defined between the head, the collar 36, and a backing plate 56 propelled by a series of pushers 58 to urge the billet into the throat defined between the rollers 42 in the head and the collar 36.

The advancing tube may be subjected to one or more operations after it leaves the throat. For instance, in FIGURE 1, the tube may be reduced in diameter and/or wall thickness by being passed through a throat defined between a core 60 which is an extension of the head and a second series of skewed rollers 62 mounted in a cage 64 journalled for rotation within a bearing block 66 and driven by gearing 68. At a second station a water spray 70 may be provided to cool the tube. At a third station, a cutting device 72 may be provided to sever the tube.

In another form, the rollers 18 are mounted on fixed axes and are driven, so that the rollers impart a twisting motion to the tube during its formation. This causes fibrous impurities to be fragmented.

The theory of tube-making by piercing requires that the contours of the skewed rollers be such that the roller meets the tube in a line contact, and, as that line contact is part of a helix, a component of force in the axial direction of the tube causes it to be propelled forwardly. The deformation imposed on the billet as it is drawn through the throat resists the advancing force provided by the rollers and it may in many cases be necessary to supplement the force tending to advance the tube by shaping the rollers to bite into the tube. For instance, in FIGURE 3, the roller 74 is hyperbolic in contour, which produces line contact when the roller is in contact with a plain cylindrical tube. However, it may be necessary or de sirable to depart from a true hyperbola by the addition of an. enlargement 76, shown in dotted lines, towards one end, that will bite into the tube as it is drawn through the throat. Where the head is conical as shown in FIG- URE 4, which is derived from FIGURE 1, the theoretical contour of the rollers must be modified to that shown at 78. An enlargement shown in chain dot at 82 is provided to bite into the tube.

In FIGURES 3 and 4, external rollers are shown. In FIGURE 5, an internal roller '84 is shown within a tube 86. The contour of the roller is again hyperbolic, but this time convex outwards, and an enlargement 88 may be provided to bite into the tube.

A development of the invention provides for the continuous drawing of tube to a theoretically infinite length, by constantly supplementing the billet as its material is used. To this end, the machine includes an enclosed annular space 90 (FIGURE 6) surrounding the head 92 and located between the collar 94 and the throat 96 and means to feed molten material 98 into the space, consisting of a reservoir 100 heated by electrical elements 102 and connected to the annular space 90 by a duct 104. The metal in the space 90 solidifies to form the billet. Thus, as the tube 106 is drawn and the billet material used, the billet is constantly supplemented by solidification of new material from the reservoir 100. While solidification must obviously take place in advance of the throat, it may be that the material may still have a measure of plasticity to facilitate deformation as the tube 106 is formed. Clearly, the greatest care must be taken in the design of the machine to ensure that metallurgically the machine is efiicient.

In the usual form of the invention the billet and the tube have no rotational forces applied between them. The forces, at least theoretically, are entirely axial (for traction) and radial, (for deformation). However, it may be advisable to gear the several skewed rollers 18 (FIG- URE 1) or 42 (FIGURE 2) together for them to rotate in unison and to ensure proper rolling with respect to the billet.

It will be well appreciated how the inconveniences of the present techniques are overcome by providing the support for the head upstream of the billet for, besides producing a concentric tube initially in a very short length of machine, the way is clear downstream to incorporate other compact means to process the tube further.

Internal attachments to the head to support the tube internally such as mandrels, rods, or holders for rollers need no longer be very rigid for, once a tube is initially produced concentrically it will naturally tend to maintain it. Externally there are no problems. Heads, rollers or other devices to process the tube externally, can be attached to the machine frame.

In a further development of the invention, a technique,

used for the manufacture of cylinders having one or both ends closed, is shown in FIGURES 7 to 11. A cylindrical billet 108 (FIGURE 7) is preformed to the cavitied shape shown in FIGURE 8. It is then propelled by a head 110 through a throat defined by the head 110 itself and a series of radially arranged skew rollers 112. The head 110 is the equivalent of the head of the previous embodiments, except that it is slidably mounted for axial movement in a guide 114 as can be seen in FIGURES 9 and 10.

Material is propelled past the rollers 112 and there results a closed-ended tube 116. The end of the tube is engaged by a tailstock 118 to steady it (FIGURES 9 and 10), and to dish it inwardly. The cylinder that forms as the billet is deformed in its passage through the annular throat between the pusher 110 and the rollers 112 is propelled partly by the rotation of the rollers and partly by the pusher (FIGURE 10). If the axes of the rollers are fixed, the pusher 110 and the tailstock 118 would be rotated. Conversely, if the axes of the rollers orbit, they would not be rotated while sliding. The length of the cylinder 116 depends only upon the volume of material available in advance of the rollers. After withdrawal of the head 110, the trailing end of the cylinder can be closed by a series of rollers 120 forced radially or axially to deform the tube end to the shape shown at 122 in FIGURE 11.

It may be necessary to heat the billet, before it enters the throat to increase the plasticity of material in the throat lest the resistance to advance through the throat be greater than the resistance to elongation of the formed tube downstream of the throat, which would lead to destruction of the article. If the function of the pusher is largely or wholly confined to support of the formed tube, and the propulsion is left preponderantly or entirely to the rollers, this danger is minimised.

This technique enables a cylinder to be made quickly and cheaply, with that uniform wall thickness which is of such importance for cylinders to contain liquids and gases under high pressure. This is due to the fact that the rollers 112 are close to the guide 114 and remain so always, so that the structure is rigid and the throat remains of uniform dimension.

The possibility of using an axially movable head, as in the machine of FIGURES 9 and 10, may lead to further developments. The advance of the head, if it is cylindrical as in FIGURES 7 to 10, produces a tube of uniform wall thickness as the radial dimension of the throat between the head and the locus of the rollers remains constant. However, if the head 110 is made tapering, its advance progressively alters the radial dimension of the throat, so that the tube being formed has an internal taper. For a tube with an outside taper, the throat may be progressively varied in radial dimension by mechanically moving the rollers 112 inwardly or outwardly as the operation proceeds. Combinations of the various systems are also included in the invention.

Furthermore, if the head 110 is made to advance with the tube, it can be left in situ in the formed tube as a lining, if the head is hollow, or as a core if it is solid. It is, therefore, possible to make a tube, say of concrete or steel, initially present as the head, with a covering of, say, plastic or lead.

FIGURE 12 illustrates the techniqueof advancing a head through a solid billet 124 to produce a tube 126 with a bulbous trailing end 128, its leading edge advancing with the free end of an axially movable head 132 into a die 134 which supports the tube and head and may size the outer surface of the tube.

As in FIGURES 9 and 10, the throat is defined by skew rollers 136 surrounding the head and which cause the forming tube to advance. The die 134 is, of course, advanced as the tube 126 advances.

Finally, a further development of the subject matter of FIGURES 7 to 11 is seen in FIGURE 13. Here a billet (its initial shape illustrated in dotted lines at 138) is trapped between a cylindrical head 140 and a series of rollers 142 that are suitably profiled, and which roll upon a backing plate 144. The billet must be sufliciently hot to be plastic, and it is deformed by the rolling to bell shape to the extent possible to the rollers. Thereafter, the rollers are withdrawn and replaced by a series of V-shaped rollers 148 and the billet is advanced through them to roll out the lower part of the bulbous zone 138 left by the first set of rollers 142. The second operation causes the bulbous zone 138 to flow into the interstices of the head and its backing plate 144. Provision is made to receive surplus metal, which enters an escape gap 152 and forms a flash 154 which is subsequently removed.

I claim:

1. Apparatus for forming a tube from an apertured billet, which apparatus comprises workpiece supporting means, constituted by a supporting surface, and feed and working means, one of the workpiece supporting means and the feed and working means being located within the other so as to define an annular working space through which the material of an apertured billet may be passed and being arranged so that the supporting surface supports the material over the entire peripheral surface where the other surface is subject to pressure from the feed and working means, the feed and working means comprising a plurality of enlarged skewed feed flanges at the inlet to the annular working space to force the material of the billet through the working space and a plurality of work rollers having a circular section working surfaces and being located downstream of the feed means in the throat.

2. Apparatus as claimed in claim 1, and means nonrotatably mounting said supporting surface.

3. The invention defined in claim 1 in which the work rollers are skewed, the feed means are feed rollers, and the feed flanges are'formed integrally with the feed rollers.

4. The invention defined in claim 3 further comprising a roller carrier which is rotatable about the axis of the supporting surface and which rotatably carries the feed rollers.

5. The invention defined in claim 1 in which the supporting surface is of circular section.

References Cited RICHARD J. HERBST, Primary Examiner 

